Until now, a signal has been sent and received to decide an appropriate photographing condition between the camera and flash devices when taking a photograph with flash by sending camera signals as camera information to the flash side and by sending signals as flash information from the flash side where it is sent to the camera side.
In this case, if exchanged information is increased, it is suitable that terminals correspond in number, as sending and receiving signals are performed through terminals installed at the point where the camera and flash devices are engaged. Recently, a camera device has been automated greatly, and its construction is complicated. For this reason, the amount of information which is exchanged between the camera side and flash side tends to increase.
However, increasing the number of terminals for sending and receiving signals, corresponding to the increased amount of information, brings about some problems. That is, the attachment area for a camera hot shoe to attach a clip-on type flash device is extremely limited. Thus, not so many terminals can be attached to the tiny hot shoe. Also, electric insulation should be considered when adding only one terminal. Therefore, it creates difficulties in manufacturing and parts cannot be replaced, as existing parts cannot be used. This is true when connecting clip-on type flash device to the camera, and the number of conductors of a wire should be increased according to the amount of information. Existing connection wires cannot be used and connector terminals do not match each other.